Web M.D. Jeanie Lerche Davis reports that a study of Chinese men found, among other things, that “Men who currently -- and formerly -- smoked were about 30% more likely to suffer from impotence.” Smoking and erectile dysfunction are both connected (individually) with plaque that builds up in the arteries: it restricts blood flow and potentially causes ED, among other problems. The habit could also be making your erections smaller.

Men’s Health reports in 8 Strategies for Stronger Erections that "In addition to damaging blood vessels, smoking may cause damage to penile tissue itself, making it less elastic and preventing it from stretching," says urologist Irwin Goldstein.

I thought that that would be a killer argument when used on male smokers--more effective than "It'll give you cancer." But no. When I told my then-wife's teenage son, who smoked (and who constantly had girls around him), about that, it had no effect on him at all.